Structured triglycerides and emulsions comprising same

ABSTRACT

The present invention relates to structured triglycerides, to parenteral nutrition emulsions of the same, and uses thereof. In particular, the invention relates to structured triglycerides that include at least one medium chain C 6 -C 12  fatty acid and at least one fatty acid selected from long chain C 14 -C 18  or very long chain C 20 -C 22  fatty acids. Preferably, each fatty acid is present in a predetermined position of the glycerol backbone. The parenteral nutrition emulsions are particularly useful for nourishing preterm- and term-infants, children, critically ill patients, and cancer patients.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 10/591,734,filed May 1, 2007, which is the 371 national state of Internationalapplication PCT/IL2005/000257 filed Mar. 3, 2005, which claims thebenefit of application No. 60/549,550 Mar. 4, 2004. The entire contentof each earlier filed application is expressly incorporated herein byreference thereto.

FIELD OF INVENTION

The present invention relates to structured triglycerides, to emulsionscomprising same suitable for parenteral nutrition, and use thereof. Inparticular, the invention relates to structured triglycerides comprisingat least one medium chain C₆-C₁₂ fatty acid and at least one fatty acidselected from long chain C₁₄-C₁₈ and very long chain C₂₀-C₂₂ fattyacids, preferably each fatty acid being in a predetermined position ofthe glycerol backbone. The parenteral nutrition emulsions areparticularly useful for nourishing preterm and term infants, children,critically ill patients, and cancer patients.

BACKGROUND OF THE INVENTION

Lipids have been used as an integral component of parenteral nutritionover the last four decades. Lipids provide essential fatty acids forcellular structures, specifically cell membranes, and for precursors ofprostaglandins, leukotrienes, thromboxanes and other eicosanoids. Theyconstitute a source of energy, take part in various biosyntheticpathways, and are carriers of fat-soluble vitamins. As such, lipids playan important role in metabolic and immune processes, in the developmentand function of the central nervous system and the retina.

Fatty acids (FA) differ from one another by the number of carbon atoms,their saturation or degree of non-saturation, the positions ofunsaturated bonds, and whether these bonds are cis or trans. All ofthese variables are relevant to the nutritional value or benefit derivedfrom triglycerides containing these acids. In addition, the enzymaticcleavage of the triglycerides is affected by the type and position ofthe fatty acids on the glycerol backbone.

Fatty acids in general are divided into four groups: short chain FA,medium chain FA (MCFA), long chain FA (LCFA), and very long chain FA(VLCFA). Fatty acids are also classified by the presence, number, andlocation of double bonds. This classification divides FA into threegroups: saturated FA (no double bonds), monounsaturated FA (one doublebond) and polyunsaturated FA (2 double bonds and more). Furtherclassification of the polyunsaturated FA is characterized by theplacement of the carbon preceding the first double bond from theterminal methyl carbon: n-3 or ω-3 FA, n-6 or ω-6 FA and n-9 or ω-9 FA.These differences determine the various characteristics of FA andtherefore their specific functions.

Lipid Emulsions

The need for lipids as essential and integral component of parenteralnutrition (PN) emerged from the observations of the clinical symptomsfollowing use of fat free PN. These clinical symptoms includedhemorrhagic dermatitis, skin atrophy, hyperglycemia, weight loss,decrease of immune function, increase of catabolism, etc.

The first generation of lipid emulsions was based on pure long chaintriglycerides (LCT) derived from soybean oil and safflower oil. Theiradministration prevented some of the symptoms of fatty acid deficiency.Nevertheless, patients that received these lipid emulsions showedimpaired function of lymphocytes and of the reticuloendothelial system,depressed T-cell counts, increased oxygen free radical production,elevation of liver enzymes, hypertriglyceridemia, and suffered frominfections.

The next generation of lipid emulsions contained 50% medium chaintriglycerides (MCT) and 50% LCT. These emulsions have many advantagescompared to pure LCT emulsions, for example, they are an efficientenergy source, they are more soluble, rapidly hydrolyzed by lipases,quickly eliminated from blood, rapidly oxidized, and have smallerparticle size. As the MCFA are all saturated, they are not subjected toperoxide formation and therefore they do not impair the immune andreticuloendothelial systems. Patients receiving MCT/LCT emulsionsdemonstrate a better nitrogen balance and a better protein sparingeffect.

Another attempt to overcome the disadvantages of pure LCT emulsions wasto use olive oil, rich in monounsaturated oleic acid (18:1 ω-9). Oliveoil based emulsions were shown to be well-tolerated, more suitable forpreventing lipid peroxidation, and maintained a normal essential FAstatus. It was also demonstrated that olive oil emulsions containprimarily alpha tocopherol, the more biologically active tocopherol,while soybean oil emulsions contain predominantly gamma tocopherol,which has little protection against lipid peroxidation. When thecomposition and peroxidation of lipoproteins were compared in childrenreceiving olive oil or soybean oil emulsions, it was found thatadministration of olive oil emulsions resulted in a decreased oxidativestress. Gobel et al., and Goulet et al., showed the advantages of oliveoil emulsions compared to other LCT emulsions in preterm infants and inchildren (Gobel Y., et al., J. Pediatr. Gastroenterol. Nutr. 37(2):161-167, 2003; Goulet, O., et al., Am. J. Clin. Nutr. 70(3): 338-345,1999). Oleic acid, and in general the ω-9 fatty acids, have been shownto contribute to brain development and function as they are a majorcomponent of the white matter and myelin.

The beneficial effects of ω-3 fatty acids derived from fish oil inenteral feeding prompted their inclusion in parenteral nutrition. Themost successful regimen was achieved by the combination of 50% MCT, 40%soybean oil and 10% fish oil. This regimen demonstrated an improvementin the immune system function of surgical and critically ill patients,an improvement of FA profile in cell membranes, anti-inflammatory andanti-coagulation effects, a normalization of plasma triglycerides (TG)and cholesterol, and a reduction in blood pressure.

Structured Triglycerides

Lipid emulsions containing randomized structured triglycerides (STG)have been obtained by mixing MCT and LCT oils and heating the mixture inthe presence of a catalyst. During this process, MCFA and LCFA can beexchanged randomly on the glycerol backbone of both oils. The new TGthus formed contains both long and medium chain FA on the same glycerol,randomly distributed. This kind of triglycerides are rapidly hydrolyzedby lipases, and hence are better cleared from the blood stream.

Many clinical studies have demonstrated the safety and the advantages ofSTG emulsions. Sandstrom et al., demonstrated that STG emulsionsadministered to postoperative patients were rapidly cleared from theplasma, rapidly oxidized, and were not associated with any side effects(Sandstrom, R., et al., JPEN 19 (5): 381-386, 1995). Provision of STGcaused a significantly higher whole body fat oxidation compared to LCT.Rubin et al, demonstrated that STG appear to be safe and well toleratedon a long term basis in patients on home parenteral nutrition andsuggested that STG emulsions may be associated with possible reductionin liver dysfunction (Rubin, M., et al., Nutrition, 16: 95-100, 2000).

Kruimel et al., compared the effect of STG versus physical mixture ofMCT and LCT on the nitrogen balance of moderately catabolicpostoperative patients. Over a period of 5 days the cumulative nitrogenbalance was less negative in the STG group (Krumiel, J. W., et al., JPEN25(5): 237-244, 2001). This difference can be explained by betterutilization of the STG fatty acids for energy and better clearance fromthe blood (ibid.). Chambrier et al., compared the effect of STG vs. aphysical mixture of MCT-LCT on liver function in postoperative patients.A significant increase in liver enzymes and in plasma TG was found tooccur in patients administered with the physical mixture of MCT-LCT,while no changes in liver function nor in plasma TG level were found tooccur in patients administered with STG (Chambrier, C., et al.,Nutrition, 15: 274-277, 1999).

U.S. Pat. No. 4,871,768 discloses a synthetic triglyceride comprising aglycerol backbone having three fatty acids attached thereto, wherein atleast one fatty acid is selected from ω3 fatty acids and at least onefatty acid is selected from C₈-C₁₀ fatty acids. The ω3 fatty acids arederived from plant oils, marine plankton oils, fungal oils, or fishoils. U.S. Pat. No. 4,871,768 also discloses a dietary supplementcomprising 10 to 40% by weight of an oily fraction, the oily fractioncomprises 10 to 90% by weight of the synthetic triglyceride. Thesynthetic triglyceride in the dietary supplement according to U.S. Pat.No. 4,871,768 further comprises ω9 fatty acids. Yet, the necessity ofdocosahexaenoic acid (DHA) and arachidonic acid in the synthetictriglyceride, and the necessity of vitamin E in the dietary supplementhave not been indicated nor the optimal ratio of ω6 to ω3.

U.S. Pat. No. 4,906,664 discloses a method for providing nutritionalsupport to patients suffering from cancer cachexia. The method comprisesthe step of parenteral administration of a diet containing a structuredlipid. The structured lipid according to U.S. Pat. No. 4,906,664 is atriglyceride wherein at least one of the chains is a medium chain fattyacid, at least one of the chains is an ω3 long chain fatty acid, and theother chain is selected from the group consisting of medium chain fattyacids and long chain fatty acids. The ratio of long chain fatty acids tomedium chain fatty acids is about 1:1. The long chain fatty acids shouldbe primarily ω3 and ω6 fatty acids, with sufficient ω6, preferably inthe form of linoleic acid.

U.S. Pat. No. 5,081,105 discloses a method of treating sarcomas in apatient through the use of nutritional support therapy comprising thestep of parenterally administering a diet including a structured lipid.The structured lipid according to U.S. Pat. No. 5,081,105 is atriglyceride where one of the chains is a medium chain fatty acid, asecond chain is a ω3 fatty acid, and the third chain is selected from H,OH, short, medium, and long fatty acids.

U.S. Pat. No. 5,962,712 discloses a family of structured lipids, one ofthe fatty acid residues is selected from the group consisting of gammalinolenic acid (GLA) and dihomogamma linolenic acid (DHGLA). A secondfatty acid residue is selected from C₁₈-C₂₂ n-3 fatty acids, and thethird fatty acid residue is selected from C₆-C₁₂ fatty acids. Thesimultaneous presence of C₁₈-C₂₂ n-3 fatty acid residues and GLA orDHGLA may serve to minimize the elongation of GLA and DHGLA toarachidonic acid. The long chain polyunsaturated n-3 fatty acids willpurportedly shift the prostaglandin metabolism away frompro-inflammatory prostanoids to non-inflammatory prostanoids, havingbeneficial effects in treating inflammation and infection. U.S. Pat. No.5,661,180 discloses a method of modulating metabolic response to traumaand disease states in a patient comprising the step of administering adietary structured lipid as disclosed in U.S. Pat. No. 5,962,712.

There is an unmet need for structured triglycerides designed to provideimproved enteral or parenteral nutrition, which is easily assimilated byinfants, children, and patients suffering severe stress or chronicillness and which is optimized to address developmental andimmunological needs.

SUMMARY OF THE INVENTION

It is now disclosed that parenteral nutrition emulsions comprisingstructured triglycerides comprising medium chain (MCFA), long chain(LCFA), and very long chain fatty acid residues (VLCFA), are highlyadvantageous for parenteral nutrition, particularly for preterm- andterm-infants, children, critically ill patients, and cancer patients.The present invention provides parenteral nutrition emulsions comprisingstructured triglycerides having specific beneficial ratios of MCFA, LCFAand VLCFA.

The present invention further provides parenteral nutrition emulsionscomprising structured triglycerides wherein the position of the fattyacid residues on the glycerol backbone is predetermined.

The present invention discloses for the first time parenteral nutritionemulsions comprising structured triglycerides comprising at least oneMCFA, and at least one LCFA or VLCFA, the LCFA or VLCFA is esterifiedprimarily at the external position of the glycerol backbone. Accordingto some embodiments, the VLCFA are selected from arachidonic acid (AA;20:4 ω-6), eicosapentaenoic acid (EPA; 20:5 ω-3), docosahexaenoic acid(DHA; 22:6 ω-3), or any combination thereof. The parenteral nutritionemulsions provide high nutritional advantage, improve the immune systemfunction, and have beneficial effects on the structure and function ofcell membranes, on the development and function of the brain, CNS andretina, on the regulation of blood pressure, and on coagulationprocesses. The parenteral nutrition emulsions of the invention are,therefore, particularly beneficial for preterm- and term-infants,children, cancer patients, and critically ill patients.

As the structured triglycerides of the present invention comprise atleast one MCFA and at least one LCFA or VLCFA on the same glycerolbackbone, the physical characteristics of these structured triglycerideemulsions are improved compared to those of pure LCT or mixed LCT/MCTemulsions. Thus, the structured triglyceride emulsions of the inventionachieve lower particle size than mixed LCT/MCT emulsions andconsequently they can be filtered through a filter of a pore size of0.22 μm. The structured triglyceride emulsions of the invention are alsomore soluble and more stable than mixed LCT/MCT emulsions. Additionally,as the LCFA and the VLCFA are located preferably at the externalposition of the glycerol backbone, the clearance of these fatty acidsfrom the blood is faster than if they were positioned on the internalposition, and therefore these structured triglycerides enablemaintenance of a regulated blood triglyceride level.

It is also disclosed that a low ratio of ω-6 to ω-3 fatty acids,particularly an ω-6/ω-3 ratio lower than 2:1 in the parenteral nutritionemulsions comprising the structured triglycerides provides beneficialeffects on brain development in preterm- and term-infants, and inchildren. The low ω-6/ω-3 ratio provides beneficial effects on theimmune system and on the heart function and these effects areparticularly essential in critically ill patients and in cancerpatients. A decrease of the ω-6 fatty acid intake and an increase of theω-3 fatty acid intake with no supplementation of sufficient amounts ofAA and DHA may impair various biological processes such as bloodcoagulation cascades and regulation of blood pressure. It may alsoimpair the chemical and physical characters of cell membranes, and thedevelopment and function of the brain, CNS, and retina. Therefore, thepresence of AA and DHA in the structured triglycerides of the inventionis of high importance both for infants, children, and adult patients.

It is further disclosed that inclusion of monounsaturated oleic acid(18:1 ω-9) in the structured triglycerides provides superior propertiescompared to polyunsaturated fatty acids, as the former is required forthe structure and function of the brain. In addition, oleic acid is lesssusceptible to peroxide formation compared to polyunsaturated fattyacids, and therefore inclusion of this fatty acid provides less exposureto peroxidation damages.

It is also disclosed that addition of vitamin E, particularly alphatocopherol, to the parenteral nutrition emulsions provides protection ofthe subject nourished with said parenteral nutrition emulsions againstperoxide formation, and therefore protects the subject from peroxidationdamages.

According to one aspect, the present invention provides a structuredtriglyceride comprising a glycerol backbone having three fatty acidresidues esterified thereto, wherein at least one fatty acid residue isselected from the group consisting of C₆-C₁₂ fatty acids and activederivatives thereof, and at least one fatty acid residue is selectedfrom the group consisting of C₁₄-C₁₈ fatty acids, C₂₀-C₂₂ fatty acids,and active derivatives thereof, with the proviso that a C₁₈-C₂₂ ω-3fatty acid residue is not present on the same glycerol backbone togetherwith gamma linolenic acid or dihomogamma linolenic acid.

According to another aspect, the present invention provides a structuredtriglyceride comprising a glycerol backbone having three fatty acidresidues esterified thereto, wherein at least one fatty acid residue isselected from the group consisting of C₆-C₁₂ fatty acids and activederivatives thereof in the internal position of the glycerol backbone,and at least one fatty acid residue is selected from the groupconsisting of C₁₄-C₁₈ fatty acids, C₂₀-C₂₂ fatty acids, and activederivatives thereof in an external position of the glycerol backbone.

According to some embodiments, the C₁₄-C₁₈ fatty acids are selected fromthe group consisting of saturated, monounsaturated, polyunsaturatedfatty acids, and any combination thereof. According to additionalembodiments, the C₁₄-C₁₈ fatty acids are selected from the groupconsisting of myristic acid (14:0), palmitic acid (16:0), palmitoleicacid (16:1), stearic acid (18:0), oleic acid (18:1 ω-9), linoleic acid(18:2 ω-6), alpha linolenic acid (18:3 ω-3), and any combinationthereof.

According to other embodiments, the C₂₀-C₂₂ fatty acids are selectedfrom the group consisting of arachidonic acid (AA; 20:4 ω-6),eicosapentaenoic acid (EPA; 20:5 ω-3), docosahexaenoic acid (DHA; 22:6ω-3), and any combination thereof.

According to another aspect, the present invention provides a parenteralnutrition emulsion composition comprising a structured triglyceride, thestructured triglyceride comprises a glycerol backbone having three fattyacid residues esterified thereto, wherein at least one fatty acidresidue is selected from the group consisting of C₆-C₁₂ fatty acids andactive derivatives thereof, and at least one fatty acid residue isselected from the group consisting of C₁₄-C₁₈ fatty acids, C₂₀-C₂₂ fattyacids, and active derivatives thereof, with the proviso that a C₁₈-C₂₂ω-3 fatty acid residue is not present on the same glycerol backbonetogether with gamma linolenic acid or dihomogamma linolenic acid.

According to a further aspect, the present invention provides aparenteral nutrition emulsion composition comprising a structuredtriglyceride, the structured triglyceride comprises a glycerol backbonehaving three fatty acid residues esterified thereto, wherein at leastone fatty acid residue is selected from the group consisting of C₆-C₁₂fatty acids and active derivatives thereof in the internal position ofthe glycerol backbone, and at least one fatty acid residue is selectedfrom the group consisting of C₁₄-C₁₈ fatty acids, C₂₀-C₂₂ fatty acids,and active derivatives thereof in an external position of the glycerolbackbone.

According to some embodiments, the parenteral nutrition emulsioncomposition comprises from about 9 to about 90% C₆-C₁₂ fatty acids basedon the weight of total fatty acids in the parenteral nutrition emulsioncomposition. According to additional embodiments, the parenteralnutrition emulsion composition comprises from about 30 to about 60%C₆-C₁₂ fatty acids based on the weight of total fatty acids in theparenteral nutrition emulsion composition. According to furtherembodiments, the parenteral nutrition emulsion composition comprisesfrom about 40 to about 50% C₆-C₁₂ fatty acids based on the weight oftotal fatty acids in the parenteral nutrition emulsion composition.According to non-limiting exemplary embodiments, the parenteralnutrition emulsion composition comprises caproic acid (6:0), caprylicacid (8:0), capric acid (10:0), and lauric acid (12:0), whichconstitute, respectively, about 0-5%, about 20-30%, about 10-30%, andabout 0-5% by weight of total fatty acids in the parenteral nutritionemulsion composition.

According to other embodiments, the parenteral nutrition emulsioncomposition comprises from about 9 to about 90% C₁₄-C₁₈ fatty acidsbased on the weight of total fatty acids in the parenteral nutritionemulsion composition. According to additional embodiments, theparenteral nutrition emulsion composition comprises from about 30 toabout 70% C₁₄-C₁₈ fatty acids based on the weight of total fatty acidsin the parenteral nutrition emulsion composition. According toadditional embodiments, the parenteral nutrition emulsion compositioncomprises from about 35 to about 55% C₁₄-C₁₈ fatty acids based on theweight of total fatty acids. According to non-limiting exemplaryembodiments, the parenteral nutrition emulsion composition comprisesmyristic acid, palmitic acid, palmitoleic acid, stearic acid, oleicacid, linoleic acid, and alpha linolenic acid, which constitute,respectively, about 0-5%, about 5-30%, about 0-5%, about 0-5%, about10-30%, about 10-30% and about 5-15% by weight of total fatty acids inthe parenteral nutrition emulsion composition.

According to additional embodiments, the parenteral nutrition emulsioncomposition comprises from about 1 to 20% C₂₀-C₂₂ fatty acids based onthe weight of total fatty acids in the parenteral nutrition emulsioncomposition. According to some embodiments, the parenteral nutritionemulsion composition comprises from about 1 to about 10% C₂₀-C₂₂ fattyacids based on the weight of total fatty acids in the parenteralnutrition emulsion composition. According to non-limiting exemplaryembodiments, the parenteral nutrition emulsion composition comprises AA,EPA, and DHA, which constitute, respectively, about 1-5%, about 0-5% andabout 1-5% by weight based on the weight of total fatty acids in theparenteral nutrition emulsion composition. It will be understood that acombination of the fatty acids disclosed hereinabove in a parenteralnutrition emulsion is highly advantageous in order to provide thenutritional needs of preterm- and term-infants, children, adults, cancerpatients, patients suffering from burns, and critically ill patients.

According to some embodiments, a majority of structured triglycerides ofthe parenteral nutrition emulsion compositions of the present inventionhave one fatty acid residue selected from the group consisting ofC₁₄-C₁₈ fatty acids, C₂₀-C₂₂ fatty acids, and active derivativesthereof, and two fatty acid residues selected from the group consistingof C₆-C₁₂ fatty acids and active derivatives thereof. According toadditional embodiments, the structured triglycerides having one fattyacid residue selected from the group consisting of C₁₄-C₁₈ fatty acids,C₂₀-C₂₂ fatty acids, and active derivatives thereof, and two fatty acidresidues selected from the group consisting of C₆-C₁₂ fatty acids andactive derivatives thereof comprise from about 80% to about 100% oftotal structured triglycerides of said emulsions.

According to other embodiments, the ratio of ω-6/ω-3 fatty acids in theparenteral nutrition emulsion composition ranges from about 7:1 to 1:1.According to additional embodiments, the ratio ranges from about 3:1 toabout 1:1. According to an exemplary embodiment, the ratio of ω-6/ω-3fatty acids in the parenteral nutrition emulsion composition ranges fromabout 2:1 to about 1.5:1. The present invention thus also encompassesratio of ω-6 to ω-3 fatty acids of 1:1.

According to some embodiments, the parenteral nutrition emulsioncompositions comprise from about 10 to about 40% (w/v) of the structuredtriglycerides of the invention. According to other embodiments, theparenteral nutrition emulsion compositions comprise from about 15 toabout 30% (w/v) of the structured triglycerides of the invention.According to an exemplary embodiment, the parenteral nutrition emulsioncompositions comprise about 20% (w/v) of the structured triglycerides ofthe invention.

According to additional embodiments, a droplet size of the parenteralnutrition emulsion compositions of the invention is lower than about 1μm. According to some embodiments, the droplet size of the parenteralnutrition emulsion compositions of the invention is lower than about0.45 μm. According to other embodiments, the droplet size is lower thanabout 0.22 μm. It will be understood that this droplet size enablesfiltering the emulsion through a membrane filter having a pore size of0.22 μm, and thus achieves higher sterilization of the emulsions.

According to other embodiments, the parenteral nutrition emulsioncomposition further comprises vitamin E. According to some embodiments,the vitamin E is alpha tocopherol. The amount of the alpha tocopherol ina parenteral nutrition emulsion of the invention is from about 0.1 toabout 5 mg per 1 g of fatty acids. Preferably, the amount of alphatocopherol is from about 1 to about 2 mg per 1 g of fatty acids.According to an exemplary embodiment, the parenteral nutrition emulsioncomprises 1.8-2.0 mg of alpha tocopherol per 1 g of fatty acids.

According to some embodiments, the parenteral nutrition emulsioncomposition further comprises an emulsifier. The amount of an emulsifiersuch as, for example phospholipids, in the parenteral nutrition emulsioncomposition is from about 0.5 to about 4% (w/v). According to additionalembodiments, the amount of the emulsifier is from about 0.5 to about2.5% (w/v). According to an exemplary embodiment, the parenteralnutrition emulsion composition comprises about 1-1.2% (w/v) ofphospholipids.

According to other embodiments, the parenteral nutrition emulsioncomposition can further comprise an osmolality modifier. An example ofan osmolality modifier is glycerin. The amount of an osmolality modifiercan range from about 1 to about 5% (w/v).

The parenteral nutrition emulsion composition can further comprise atleast one component selected from the group consisting of surfactants,carbohydrate nutrients, electrolytes, amino acids, vitamins, traceminerals, preservatives and water. The parenteral nutrition emulsioncomposition can also comprise sterile water.

According to certain non-limiting embodiments, the parenteral nutritionemulsion composition comprises:

-   -   (a) about 20% (w/v) structured triglycerides comprising:        -   about 40-50% by weight C₆-C₁₂ fatty acids based on the            weight of total fatty acids, wherein the C₆-C₁₂ fatty acids            comprise 0-5% caproic acid, 20-30% caprylic acid, 10-30%            capric acid, and 0-5% lauric acid based on the weight of            total fatty acids;        -   about 35-55% by weight C₁₄-C₁₈ fatty acids based on the            weight of total fatty acids, wherein the C₁₄-C₁₈ fatty acids            comprise 0-5% mystiric acid, 5-30% palmitic acid, 0-5%            palmitoleic acid, 0-5% stearic acid, 10-30% oleic acid,            10-30% linoleic acid, and 5-15% alpha linolenic acid based            on the weight of total fatty acids; and        -   about 4.5-5.5% by weight C₂₀-C₂₂ fatty acids based on the            weight of total fatty acids, wherein the C₂₀-C₂₂ fatty acids            comprise 1-5% AA, 0-5% EPA, and 1-5% DHA based on the weight            of total fatty acids, wherein the ratio of ω-6 to ω-3 fatty            acids is about 1:1-2:1;    -   (b) about 1.2% (w/v) phospholipids;    -   (c) about 1.8-2.0 mg/1 g of fatty acids alpha tocopherol;    -   (d) about 10-25 g/L glycerin; and    -   (e) water.

According to another exemplary embodiment, the parenteral nutritionemulsion composition comprises:

-   -   (a) about 20% (w/v) structured triglycerides comprising:        -   about 45% by weight C₆-C₁₂ fatty acids based on the weight            of total fatty acids, wherein the C₆-C₁₂ fatty acids            comprise 2.5% caproic acid, 30% caprylic acid, 10% capric            acid, and 2.5% lauric acid by weight based on the weight of            total fatty acids;        -   about 50% by weight C₁₄-C₁₈ fatty acids based on the weight            of total fatty acids, wherein the C₁₄-C₁₈ fatty acids            comprise 10% palmitic acid, 2.5% stearic acid, 15% oleic            acid, 16% linoleic acid, and 7% alpha linolenic acid by            weight based on the weight of total fatty acids; and        -   about 5% by weight C₂₀-C₂₂ fatty acids based on the weight            of total fatty acids, wherein the C₂₀-C₂₂ fatty acids            comprise 1.5% AA, 1.5% EPA, and 1.5% DHA by weight based on            the weight of total fatty acids, wherein the ratio of ω-6 to            ω-3 fatty acids is 1.75;    -   (b) about 1.2% (w/v) phospholipids;    -   (c) about 1.8 mg/1 g of fatty acids alpha tocopherol;    -   (d) about 10-25 g/L glycerin; and    -   (e) water.

According to a further aspect, the present invention provides a processof synthesizing a structured triglyceride of the invention comprisingthe step of performing an acidolysis reaction. According to someembodiments, the acidolysis reaction is catalyzed by a lipase. Accordingto additional embodiments, the triglyceride is a medium chaintriglyceride. According to additional embodiments, the fatty acid isselected from the group consisting of C₁₄-C₁₈ fatty acids, C₂₀-C₂₂ fattyacids, and active derivatives thereof. According to additionalembodiments, the process of synthesizing the structured triglyceride ofthe invention further comprises the step of distilling the reactionmixture to remove non-reacted MCT and fatty acid.

According to another aspect, the present invention provides a process ofpreparing a parenteral nutrition emulsion composition comprising thestep of reducing the droplet size of the emulsion below of about 1 μm.According to some embodiments, the droplet size is reduced below 0.45μm. According to non-limiting exemplary embodiments, the droplet size isreduced below 0.22 μm.

According to another aspect, the present invention provides a method ofproviding nutrition to a subject in need thereof comprising parenterallyadministering to the subject a parenteral nutrition emulsion compositionof the invention.

According to some embodiments, the subject to be nourished by theparenteral nutrition emulsion composition of the invention is a preterminfant, a term infant, a child, an adult, a critically ill patient, acancer patient, or a patient suffering from surgical trauma, burns,malnutrition, starvation, aging, or immunosuppression. According toother embodiments, the subject to be nourished by the parenteralnutrition emulsion of the invention is a patient suffering from AIDS.

These and other embodiments of the present invention will be betterunderstood in relation to the description, examples, and claims thatfollow.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a schematic presentation of the lipase-catalyzed acidolysisreaction between MCT and free fatty acids in solvent-free system. Mrepresents medium-chain fatty acyl group and Lc represents long-chain orvery long chain fatty acyl group.

FIGS. 2A-B show HPLC chromatograms of MCT before and after an acidolysisreaction. FIG. 2A, peak 1 represents the free fatty acid, namelypalmitic acid while peaks 2, 3, 4 and 5 represent the MCT before thereaction and peak 6 is trilaurin, an internal standard. FIG. 2B, peaks1, 2 and 3 represent the liberated medium-chain fatty acids, while peak4 represents the non-reacted palmitic acid. Peaks 5, 6, 7 and 8represent the non-reacted MCT in the reaction medium, while peaks 9, 10,and 11 represent the new products containing one long-chain fatty acylgroup. Peaks 12 and 13 represent the new products containing twolong-chain fatty acyl groups.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides structured triglycerides and parenteralnutrition emulsions comprising same useful in parenteral nutrition ofpreterm- and term-infants, children, adults, critically ill patients,and cancer patients.

According to one aspect, the present invention provides a structuredtriglyceride comprising a glycerol backbone having three fatty acidresidues esterified thereto, wherein at least one fatty acid residue isselected from medium chain fatty acids and active derivatives thereof,and at least one fatty acid residue is selected from the groupconsisting of long chain fatty acids, very long chain fatty acids, andactive derivatives thereof, with the proviso that a C₁₈₋₂₂ ω-3 fattyacid residue is not present on the same glycerol backbone together withgamma linolenic acid or dihomogamma linolenic acid.

The term “active derivatives” as used herein includes esters, ethers,amines, amides, substituted fatty acids (e.g., halogen substituted fattyacids), and other substitutions, which do not affect the beneficialproperties of the fatty acids.

The term “ω-3”, “ω-6” and “ω-9” as used herein refers to a fatty acid inwhich a double bond is present at the third carbon, sixth carbon, andninth carbon, respectively, from the methyl end of the hydrocarbonchain. This nomenclature is equivalent to the n-3, n-6, and n-9designations. Thus, the terms ω-3, ω3, and n-3; ω-6, ω6, and n-6; andω-9, ω9, and n-9 are used interchangeably throughout the specificationand claims of the present invention.

The structured triglycerides of the invention are made as “designeroils”. Using enzymatic procedures known in the art that direct theincorporation of specific fatty acids to specific positions in theglycerol molecule, structured triglycerides are synthesized.

U.S. Pat. No. 6,537,787, the content of which is incorporated byreference as if fully set forth herein, discloses a method for obtaininga mixture enriched with polyunsaturated fatty acid triglycerides in thepresence of a position-specific lipase, particularly 1,3-specificlipase. The specific lipase according to U.S. Pat. No. 6,537,787 ispreferably a Candida antarctica lipase.

U.S. Pat. No. 6,518,049, the content of which is incorporated byreference as if fully set forth herein, discloses a process foresterifying a marine oil composition containing EPA and DHA as freefatty acids to form a free fatty acid fraction enriched in at least oneof these fatty acids as compared to the starting composition, comprisingthe step of reacting the marine oil composition with glycerol in thepresence of a lipase catalyst under reduced pressure and essentiallyorganic solvent-free conditions, and recovering a free fatty acidfraction enriched in at least one of EPA and DHA. According to U.S. Pat.No. 6,518,049 the lipase is preferably immobilized on a carrier and isRhizomucor miehei lipase.

Sugihara et al. (Appl. Microbiol. and Biotech. 1993 40:279-83 andreferences cited therein) disclosed a microorganism having a moderateselectivity towards the sn-2 position in glycerides. Ota et al. (Biosci.Biotechnol. Biochem. 2000, 64: 2497) disclosed an enzyme of Geotrichumcandidum, which hydrolyzes the sn-2-positioned ester bond nearly twicemore as compared to hydrolysis of the 1- or 3-positioned ester bonds.

U.S. Pat. No. 6,605,452 to Basheer, the content of which is incorporatedby reference as if fully set forth herein, discloses a lipasepreparation immobilized onto an insoluble matrix that preferably has1,3-positional specificity with respect to triacylglycerols.

Thus, according to the principles of the present invention, a lipase canbe used in a crude form, e.g., as supplied by a manufacturer or asisolated by any method known in the art for isolation of lipases, or alipase or a surfactant-coated lipase complex can be immobilized on aninsoluble matrix and subsequently used for preparing the structuredtriglycerides of the present invention. The lipase can be derived fromany source, though a preferable source is a microorganism. Manydifferent species can be used as a source of the lipase including, butnot limited to, Aspergillus niger, Aspergillus oryzae, Burkholderia sp.,Candida antarctica such as Candida antarctica A and B, Candidacylindracea, Candida lipolytica, Candida rugosa, Chromobacteriumviscosum, Humicola sp., Lipoprotein lipase Pseudomonas A, Mucorjavanicus, Mucor miehei, Penicillium roqueforti, Pseudomonasfluorescens, Pseudomonas Cepacia, Porcine pancreatic lipase (PPL),Rhizopus arrhizus, Rhizopus javanicus, Rhizopus japonicus, Rhizopusoryzae, Rhizopus miehei, and Rhizopus niveus, Thermomyces lanuginose,and Wheat germ lipase. The lipases used for the production of thestructured triglycerides of the invention have 1,3-positionalspecificity with respect to the structured triglyceride.

Structured triglycerides of this invention can be prepared by variousmethods as are well known in the art. The structured triglycerides canbe prepared by esterification of fatty acids and glycerol, acidolysis,transesterification and interesterification. In the specification andthe claims that follow the term acidolysis includes reactions betweenone or more free fatty acid and a triglyceride to exchange at least onefatty acid of the triglyceride with at least one of the free fattyacids. According to some embodiments acidolysis is performed by reactingMCT and free fatty acids (i.e., reaction of the free fatty acids withMCT to exchange one or more of the MCFA). In the specification and theclaims that follow the term transesterification includes reactionsbetween two distinct triglycerides to exchange at least one fatty acidof the first triglyceride with at least one of the fatty acids of thesecond triglyceride. According to some embodiments transeterification isperformed by reacting an MCT and an LCT. In the specification and theclaims that follow the term interesterification includes reactions of atriglyceride with an alkyl ester of a fatty acid. According to someembodiments the interesterification reaction of the fatty acid alkylester is with an MCT to exchange one or more of the MCFA. The fatty acidalkyl ester is typically though not exclusively a methyl or ethyl fattyacid ester. According to some embodiments the reaction is catalyzedusing a lipase preparation. It should also be noted that contacting alipase preparation with fatty acid-containing substrates may be effectedwithin a reaction reactor, e.g., a tank reactor or a fixed-bed reactor.It will be understood that any method known in the art for preparing thestructured triglycerides is encompassed in the present invention.

Typically, the structured triglycerides of the invention can be preparedby acidolysis reaction between MCT and free fatty acids using lipases assupplied by the manufacturers or immobilized on an insoluble matrix. Forimmobilization of the lipases, an insoluble matrix, such as a silicateor an ion-exchange resin, is used and the lipases are immobilized fromtheir aqueous solutions. Wet immobilized lipases are pretreated with amixture of biphase medium containing phosphate buffer solution and oiland then dried under vacuum to reduce the water content of theimmobilized lipase down to less than 2 wt %. Lipases can also beimmobilized and activated according to procedures well known in the art.For example, immobilized and activated lipases possessing acidolysisactivity can be prepared by attaching a polyethylene group to thesurface functional group of the enzyme according to U.S. Pat. No.4,645,741 to Inada et. al. Lipases can also be activated and immobilizedaccording to the procedure described by Boosley et al. (U.S. Pat. No.5,232,843) where a lipase is immobilized on a hydrophobic surface, e.g.,silica or an ion-exchange resin, precoated with a non-lipase protein.Immobilized lipases on a dry, porous particulate hydrophobic support andcontaining a surfactant prepared according to U.S. Pat. No. 5,773,266and U.S. Pat. No. 6,596,520, can also be applied for producing thestructured triglycerides of the present invention.

Additionally or alternatively, other methods for preparing structuredtriglycerides of the present invention can involve the use of alkalimetal catalysts such as sodium, and/or nucleophilic catalysts, such ashydroxides and alkoxides, which function to randomly exchange fattyacids on the glycerol backbone of the glycerol molecule.

Inclusion of C₆-C₁₂ fatty acids in the structured triglycerides has somebenefits. The C₆-C₁₂ fatty acids do not need carnitine to enter themitochondria, thus they are rapidly cleared from blood and are used asenergy source. As a component of the structured triglycerides, MCFAcontribute to achieve a lower molecular weight, better solubility andbetter stability of the emulsion.

According to another aspect, the present invention provides a parenteralnutrition emulsion comprising the structured triglyceride of theinvention. It is apparent to a person skilled in the art that thepresent invention encompasses nutrition emulsions comprising thestructured triglycerides of the invention for enteral nutrition.

According to some embodiments, the parenteral nutrition emulsion furthercomprises vitamin E, preferably alpha tocopherol. The normal range ofplasma tocopherol concentrations is between 0.7 and 1.6 mg/100 ml.Generally, the recommended amount of vitamin E for premature infants is4.55 mg/day and for adults it is 100-200 mg/day. Vitamin E is classifiedas a practically non-toxic substance. A dosage below 1000 mg/day is safeand free from side effects. In order to maintain normal range oftocopherol, vitamin E should be matched quantitatively to unsaturatedFA. Therefore, the parenteral nutrition emulsion of the invention cancomprise 0.1 to 5 mg of alpha tocopherol per 1 g of fatty acids.Preferably, the parenteral nutrition emulsion can comprise 1 to 2 mg ofalpha tocopherol per 1 g of fatty acids.

The parenteral nutrition emulsion composition according to the inventioncan advantageously further comprise a natural biologically compatibleemulsifier. The emulsifier is preferably a phospholipid compound or amixture of phospholipids, such as lecithin, phosphatidylcholine,phosphatidyl ethanolamine or mixtures thereof. Non-limiting examples ofphospholipids which can be used in the compositions of the invention arelecithins; EPIKURON 170® being a mixture of about 70% (w/v) ofphosphatidylcholine, 12% phosphatidylethanolamine, and about 16% otherphospholipids, or OVOTHIN 160® being a mixture comprising about 60%(w/v) phosphatidylcholine, 18% (w/v) phosphatidylethanolamine, and 12%(w/v) other phospholipids, both manufactured by Lucas Meyer (Germany).These mixtures of mainly phosphatidylcholine andphosphatidylethanolamine are derived from a natural source, such aspurified egg yolk phospholipids (for the Ovothin series) and soybean oilphospholipids (for the Epikuron series); a purified phospholipidmixture; LIPOID E-80® being a phospholipid mixture comprising about 80%(w/v) phosphatidylcholine, about 8% (w/v) phosphatidylethanolamine,about 3.6% non-polar lipids, and about 2% sphingomyeline, manufacturedby Lipoid KG (Ludwigshafen, FRG). Other phospholipids of plants (e.g.,lecithin) or of animal origin known in the art can be used asemulsifiers for the preparations of the parenteral nutrition emulsioncompositions of the invention. For example, other forms of emulsifierscontaining fatty acyl groups, such as polyol fatty acid esters, can beused for the preparations of such emulsions.

The emulsion can further comprise a pharmaceutically acceptablenon-natural surfactant. Any conventional pharmaceutically acceptablenon-ionic surfactant can be used. Generally, the surfactant is anon-ionic alkylene oxide condensate of an organic compound, whichcontains one or more hydroxyl groups. For example, ethoxylated and/orpropoxylated alcohol or ester compounds or mixtures thereof are commonlyavailable and are well known to those skilled in the art. Suitablesurfactants include, but are not limited to, TYLOXAPOL; POLOXAMER 4070;POLOXAMER 188; POLYOXYL 40 Stearate; POLYSORBATE 80, and POLYSORBATE 20,as well as various compounds sold under the trade name TWEEN (ICIAmerican Inc., Wilmington, Del., U.S.A.), PLURONIC F-68 (trade name ofBASF, Ludwigshafen, Germany for a copolymer of polyoxyethylene andpolyoxypropylene). Preferred surfactants also include polyoxyethylatedoils or poloxamines. The TYLOXAPOL and TWEEN surfactants are mostpreferred because they are FDA approved for human use.

The parenteral nutrition emulsion composition can further comprisecarbohydrate nutrients such as, for example, dextrose; electrolytes suchas, for example, potassium and sodium chloride; amino acids includingessential and non-essential amino acids; vitamins such as, for example,vitamin A, and vitamin D; trace minerals such as, for example, zincions; and a preservative such as, for example, methyl-, ethyl-, propyl-,and butylparaben, which are medically accepted for parenteraladministration.

The parenteral nutrition emulsion composition can further comprise anosmolality modifier such as glycerin, sorbitol, or alanine (see, forexample, U.S. Pat. No. 4,567,045, the content of which is incorporatedby reference as if fully set forth herein), and sterile water.

Generally, lipid droplets in emulsions for medical use should preferablybe small, i.e., below about 1 μm, since the smaller the droplets, themore stable the emulsion is in storage. The droplet size isadvantageously in the size range of about 0.05 to 0.5 μm, and preferablyabout 0.1 to 0.3 μm. The droplet size is of particular importance sincelarge droplets will not readily pass through small blood capillaries andwill not pass through a filter required for filtration of the emulsionbefore its administration to a subject in need thereof. The compositionsof the invention are particularly suitable for obtaining such smalldroplets.

The emulsions of the present invention can be prepared by a number ofways. In accordance with one preparation method, an aqueous solution andan oily solution are separately prepared, the aqueous solutioncomprising the phospholipids and optionally also an osmotic pressureregulator and a preservative, and the oily solution comprising thestructured triglycerides, and an antioxidant. The aqueous solution isprepared from two premade solutions: a first, alcoholic solutioncontaining the phospholipids and a second solution containing the otheroptional ingredients mentioned above in water. The aqueous solution isthen prepared by mixing the first and the second solutions, and removingthe alcohol, for example by evaporation, to yield the aforementionedaqueous solution.

The aqueous solution and the oily solution are then mixed with oneanother. However, the so-obtained mixture does not yet consist ofsufficiently small droplets, the size of which (obtained after mixingwith a magnetic stirrer) is about 10 μm. The droplet size of theinventive emulsion can then be decreased by the use of emulsificationequipment such as UltraTurrax (Jankl and Kunkel, Staufen, FRG), whichyields droplets having an average diameter of about 1.1 μm, or of a highshear mixer, e.g., Polytron (Kinematica, Lucerne, Switzerland), whichyields droplets having an average diameter of about 0.65 μm.

Especially small droplets can be obtained in the inventive emulsions byutilizing a two-stage pressure homogenizer in which the crude dispersionis forced under high pressure through the angular space between a springloaded valve and the valve seat, the second stage being in tandem withthe first so that the emulsion is subjected to two very rapid dispersionprocesses. An example of such an apparatus is the Gaulin Homogenizer(APV Gaulin, Hilversum, The Netherlands). Use of such an apparatus inaccordance with the invention yields emulsions in which the dropletshave an average diameter of about 0.27 μm with a relatively smalldeviation.

Even smaller droplets can be obtained when the emulsification processcombines the use of both a Polytron-type high shear mixer followed byhomogenization. The droplet size, which is obtained in such acombination, is about 0.1-0.15 μm. These relatively small size dropletsare preferred when the emulsion is to be used for intravenousadministration or when the formulation is to be sterilized byfiltration.

According to some embodiments, the emulsions of the present applicationare prepared by applying a high shear mixer (Ultraturrax) for 5 min at amixing rate of 10,000 RPM. Emulsions obtained after this stage arefurther treated with a microfluidizer at a pressure typically in therange of 800-2600 bar for five minutes at room temperature. Thereafter,the emulsions are cooled to room temperature and the mean droplet sizeis lower than 0.2 μm. Emulsions obtained after the aforementionedtwo-stage process are sterilized by filtration using a membrane filterhaving a pore size of less than 0.45 μm, and preferably less than 0.2μm. The pH in the emulsion is adjusted to a physiologically accepted pH,typically pH of 6 to 8, with 0.5M NaOH or 0.5 M HCl solutions.

Another method for preparing the parenteral nutrition emulsioncompositions of the invention is by mixing together a liposome mixtureand an oily mixture, each one prepared separately beforehand. Theliposome mixture comprises all the ingredients, which in the finalcomposition do not form part of the oily phase, namely thephospholipids, and also the optional osmotic pressure regulator and thepreservative. The preparation of the liposome mixture from theseingredients can be carried out by means known in the art.

The oily mixture comprises the structured triglycerides, and also theanti-oxidant.

After the liposome mixture is mixed together with the oily mixture, anemulsion is formed having relatively large droplets, e.g., about 10 μm,which is further processed in a similar manner as described above inconnection with the first preparation method, until an emulsion havingfine homogenous droplets is obtained.

Typically, the emulsions of the present invention are filtered through amembrane filter having a pore size of less than 0.45 μm, preferably amembrane filter having a pore size of 0.2 μm. The emulsions are furthersterilized by heating up to 121° C. for 15 min under inert gasatmosphere such as, for example, nitrogen, while rotating the emulsionduring autoclaving. However, any method for sterilization as known inthe art is encompassed in the present invention.

Distillation of the structured triglycerides is performed by heating andevaporating the structured triglycerides, preferably under vacuum.Preferably, the structured triglycerides of the present invention aresubjected to molecular or short-path distillation, which is performed atlow temperature under very low pressure, typically below 0.01 mm Hg.Preferably, the distillation is conducted at a temperature of 120° C. to230° C. The pressure can vary from about 1×10⁻³ kPa to 0.533 kPa. Thislow pressure enables the separation of high molecular weight compoundssuch as the structured triglycerides of the invention. Free fatty acidscan also be removed from the reaction mixture by washing with a sodiumhydroxide or an alkoxide solution, preferably of about 0.5M.Alternatively or additionally, the free fatty acid can also be removedfrom the reaction mixture by steam stripping.

The emulsions of the present invention are packaged and stored inhermetically sealed containers for long or short-term storage. Theadditives to be included in the emulsions will depend upon how long theemulsions are to be stored. Long-term storage is acceptable foremulsions with aqueous phases containing sugar, the amino acids and someelectrolytes. Dextrose should not be included in emulsions prepared forlong-term storage.

Advantages of Different Classes of Fatty Acids

The group of medium chain fatty acids (MCFA) includes fatty acids thatconsist of 6-12 carbon atoms. Their chemical and physical structuremakes the MCFA more soluble than long or very long chain fatty acids(LCFA or VLCFA, respectively); the latter terms denote fatty acid of14-18 and 20-22 carbon atoms, respectively. All the fatty acids in theMCFA group are saturated. Being rapidly oxidized, MCFA are considered asa very good source of energy.

Emulsions containing medium chain triglycerides (MCT) are more stablethan those containing pure long chain triglycerides (LCT). As MCT enterthe blood stream, lipases cleave the triglycerides hydrolytically toglycerol and free fatty acids. Since MCFA do not need carnitine to enterthe mitochondria, the bulk of FA released is immediately taken up by thetissues and rapidly oxidized. This metabolic pathway enables MCFA to beeliminated from the blood stream more quickly than LCFA, and as suchthey do not increase blood triglyceride levels and they have lowtendency of incorporation into tissue lipids. MCFA are also known topreserve body protein, to increase nitrogen retention, to decreasegluconeogenesis, and to improve nitrogen balance. MCFA are, therefore,used as a rapid energy source.

LCFA consist of 14-18 carbon atoms. They can be saturated,monounsaturated or polyunsaturated. Long chain triglycerides aretransported in the blood as lipoproteins. Lipoprotein lipase and hepaticlipase hydrolyze LCT to FA and glycerol. The clearance of LCT from theblood is slower than MCT. LCFA enter the mitochondria by carnitine. LCFAfunction as an energy source by beta oxidation, as precursors of longerchain FA, and as a storage in adipose tissues. The most important LCFAare linoleic acid (18:2 ω-6) and alpha linolenic (18:3 ω-3), bothconsidered essential FA since they cannot be synthesized by the humanbody, and therefore must be provided in the diet.

The group of very long chain fatty acids (VLCFA) includes chains of 20carbon atoms or more. Most of the VLCFA are polyunsaturated. They aresynthesized from LCFA by elongation process, which involves severalenzymes. Among the most important VLCFA are arachidonic acid (AA), anω-6 fatty acid, and docosahexaenoic (DHA), an ω-3 fatty acid, which havebeen shown to be necessary for normal development and function of thebrain, the central nervous system (CNS) and the retina. AA and DHA arenot only mechanical components of the CNS structure, but also requiredfor cell signaling systems in neurons. There is evidence linking DHAdeficiency to attention deficit and hyperactivity disorders, dyslexia,senile dementia, reduced visual and cognitive function, clinicaldepression, schizophrenia and other problems of psychological andphysiological nature. In addition, eicosapentaenoic acid (EPA) and DHA,both ω-3 fatty acids, have been indicated to have beneficial effects oncoronary heart disease, hypertension, inflammation, arthritis,psoriasis, and other autoimmune disorders and cancer. DHA and AA arealso involved in the synthesis of prostaglandins, thromboxanes andleukotrienes. In addition, DHA and AA are crucial components ofbiological cell membranes. It has been well established that fetus,preterm and term infants require these fatty acids for their normaldevelopment.

Incorporation rates of DHA and AA in red blood cell membranes of infantswere shown to decline without supplementation of DHA and AA. Infants fedwith human milk (which contains DHA and AA) or formula supplemented withthose fatty acids, were shown to maintain normal rates of incorporation.Other studies show that term and preterm infants fed with formulacontaining VLCFA exhibit better cognitive behavior and psychomotordevelopment than term and preterm infants fed with formula that did notcontain VLCFA.

The effect of ω-3 VLCFA, like DHA and EPA, on the immune system has beenstudied in animals and humans. Surgical patients that were givenparenteral nutrition including DHA and EPA showed a rise in interleukin2 Patients having inflammatory bowel diseases who received parenteral orenteral nutrition containing DHA and EPA, showed an improvement in theirclinical state with a reduction of the steroid intake. These beneficialeffects of VLCFA ω-3 on inflammatory diseases is presumably due to theirinvolvement in interleukin production, which suppress inflammatoryprocesses.

The VLCFA ω-3 have also been shown to exert beneficial effect oncoronary heart diseases as they reduce platelet aggregation and bloodviscosity, increase capillary flow, and reduce the risk of myocardialinfarction. It should be appreciated that the rate of conversion ofthese very long chain fatty acids from their precursors is not adequateto fulfill the body requirements, and therefore such fatty acids have tobe included in parenteral nutrition.

According to the principles of the present invention, at least part ofthe triglycerides incorporated into the parenteral nutrition emulsioncomprise ω-6 fatty acids. It will be appreciated that among the ω-6VLCFA, AA is one of the more preferred ω-6 fatty acids. According to theprinciples of the present invention, although the structuredtriglycerides can comprise any ω-6 fatty acid, gamma linolenic acid anddihomogamma linolenic acid are not present simultaneously on the sameglycerol backbone with C₁₈₋₂₂ n-3 fatty acid residue.

Vitamin E

Vitamin E is the nutritional designation of the tocopherols, a group ofessential biologically active substances. The various tocopherols arefound in germinal cells of plants, in egg yolk, and in meat. The naturaltocopherols include four isomers: alpha, beta, gamma, and delta. Themost biologically active vitamin E is the alpha tocopherol isomer.

Consumption of fatty acids containing double bonds increases the hazardof peroxide formation, which leads to structural changes within cellularmembranes. These changes are demonstrated particularly in impairment ofthe immune system function, in pulmonary complications, and in increasedhemolysis.

Preterm infants and critically ill patients are more vulnerable toperoxidation hazards. Vitamin E is a highly effective antioxidant,protecting the double bonds of unsaturated fatty acids from oxidativedestruction. This protective function is demonstrated both in vitro, inlipid emulsions, and in vivo, by protecting the lipid fracture ofmembranes.

Vitamin E is also essential for the maintenance of a functional immunesystem. In vitamin E deficiency there is a decrease in the resistance toinfection, in the immune response, in the activation of T lymphocytes,in the production of interleukin 2, and in the phagocytic capacity.Patients receiving lipid emulsion in parenteral nutrition have anincreased requirement for vitamin E.

The following examples are to be considered merely as illustrative andnon-limiting in nature. It will be apparent to one skilled in the art towhich the present invention pertains that many modifications,permutations, and variations may be made without departing from thescope of the invention.

Example 1 Identification of Lipases Suitable for Synthesis of StructuredTriglycerides Materials and Methods

MCT solution was purchased from (Croda, Singapore). The MCT solutioncontained 58% Caprylic acid and 42% Capric acid. According to themanufacturer, both fatty acids are distributed randomly on the glycerolbackbone. Free fatty acids of different purities were purchased fromSigma. DHA and EPA were obtained from K.D. Pharma, Germany. Arachidonicacid bound to glycerol in a form of triglycerides was obtained fromMartek, USA, at a concentration of 20%. All solvents and chemicals wereobtained from Sigma and were of analytical grade. Lipases were purchasedfrom Sigma, USA.

Acidolysis Reaction

The acidolysis activity of crude enzymes and enzymes adapted forsynthetic reactions was assayed by adding an enzyme preparation (500 mg)into a 10 ml reaction solution containing MCT and a free fatty acidwhere the molar ratio between both substrates was 1:1. The reactionmixture was shaken for 16 hours at a temperature of 50° C. Samples (0.1ml) were taken from the reaction mixture and mixed with 10 ml solventcomprised of acetone-dichloromethane at a ratio of 90:10. The sampleswere filtered through a Millipore filter (pore size 0.45 μm) and theninjected to the HPLC. The reaction is presented in FIG. 1.

Analysis

The reaction progress was followed by analyzing the triglyceridecomposition in the reaction medium before and after the enzymaticreaction using an HPLC equipped with an ELSD (Evaporative lightScattering Detector). The HPLC was equipped with a LiChrosorb CH-18Super (250×4 mm, 5 μm, MERCK). The HPLC running conditions were asfollows: mobile phase A, Acetonitrile/Dichloromethane/Acetone (80/15/5);mobile phase B: Acetone/Dichloromethane/Acetone (20/60/20). The flowrate was 1 ml/min and the gradient was 0 to 100% B for 30 min.

FIGS. 2A and 2B show HPLC chromatograms before and after acidolysisreaction of MCT. FIG. 2A, peak 1 represents the free fatty acid, namelypalmitic acid while peaks 2, 3, 4 and 5 represent the MCT before thereaction and peak 6 is trilaurin, an internal standard. FIG. 2B, peaks1, 2 and 3 represent the liberated medium-chain fatty acids, while peak4 represents the non-reacted palmitic acid. Peaks 5, 6, 7 and 8represent the non-reacted MCT in the reaction medium, while peaks 9, 10,and 11 represent the new products containing one long-chain fatty acylgroup. Peaks 12 and 13 represent the new products containing twolong-chain fatty acyl groups.

The substrate conversion was calculated as follows:

Conversion %=100×(Sum of area of the 4 peaks representing the MCT attime zero)−(Sum of area of the 4 peaks representing the MCT after 16hreaction time)per Sum of area of the 4 peaks representing the MCT attime zero.

The MCT conversion (%) was used as an indicative parameter for theefficiency of enzyme activity to obtain the desired product.

Results

Tables 1-12 show the acidolysis activity of various lipases, which werescreened for their ability to catalyze the reaction between MCT and freefatty acids in a solvent-free system according to the enzymaticallycatalyzed reaction presented in FIG. 1. All lipases were used in theircrude form as supplied by the manufacturer (Sigma) or immobilized on aninsoluble matrix. Immobilized lipases were activated before their use inthe acidolysis reaction containing MCT and a long-chain fatty acid bypretreatment with a biphase system containing 50% triglyceride oil suchas olive oil, soy oil and the like and 50% water. This pretreatment leadto the activation of the immobilized enzymes for synthetic applications.

A typical enzyme activation and immobilization procedure used in thisexample is as follows: 1 g of a crude lipase preparation was dissolvedin a 1 L of phosphate buffer solution of an appropriate pH according tothe recommendation of the enzyme's manufacturer. 10 g of support matrix(silica, celite, an ion-exchange resin such as DUOLITE® A56, DUOLITE®A7, DUOLITE® XAD761, or Amberlite™ XAD16) were added into the stirredenzyme solution. The slurry was shaken for 8 hours at a temperature of10° C. Hundred ml of cold acetone was optionally added into the stirredslurry in order to enhance the enzyme immobilization on the matrixsurface. The immobilized enzyme was filtered of from the mixture andthen freeze-dried or used wet for the following step. One g offreeze-dried immobilized lipase (water content of less than 2 weight %)or wet immobilized lipase (water content of approx. 20%) was added intoa biphase system comprised of 5 g olive oil and 2 g buffer solution ofpH7 at room temperature. The mixture was stirred for 10 min. Theimmobilized lipases was filtered of from the mixture, washed with coldacetone, dried in a desiccator and then used for the acidolysis reactionbetween MCT and a fatty acyl donor.

TABLE 1 The acidolysis activity of different enzymes using MCT andcaproic acid. Lipase origin Conversion % (24 h) Aspergillus niger 5Candida Antarctica 30 Candida cylindracea 2 Mucor miehei 35 Pseudomonasfluorescens 4 Pseudomonas cepacia 27 Rhizopus arrhizus 42 Rhizopusniveus 3 Porcine pancreas lipase 6 Aspergillus oryzae 8 Candidalipolytica 8 Mucor javanicus 32 Penicillium roqueforti 3 Rhizomucormiehei 31 Wheat germ 2 Chromobacterium viscosum 18 Lipoprotein lipasePseudomonas A 17 Lipoprotein lipase Pseudomonas B 18

Reaction conditions: MCT (1 gr), caproic acid (0.23 gr), and 500 mgenzyme preparation. The reaction mixture was shaken and thermostated at50° C. for 16 h.

The results presented in Table 1 show that there are 6 differentpreferred sources for lipases for the acidolysis reaction of Caproicacid and MCT. These sources of lipases include Candida Antarctica, Mucormiehei, Pseudomonas cepacia, Rhizopus arrhizus, Mucor javanicus andRhizomucor miehei. Other lipases extracted form different sources ofmicroorganisms did not show adequate acidolysis activity in organicmedium.

TABLE 2 The acidolysis activity of different enzymes using MCT andCaprylic acid. Lipase origin Conversion % (24 h) Aspergillus niger 3Candida Antarctica 34 Candida cylindracea 5 Mucor miehei 42 Pseudomonasfluorescens 6 Pseudomonas cepacia 32 Rhizopus arrhizus 38 Rhizopusniveus 2 Porcine pancreas lipase 5 Aspergillus oryzae 9 Candidalipolytica 3 Mucor javanicus 37 Penicillium roqueforti 5 Rhizomucormiehei 37 Wheat germ 6 Chromobacterium viscosum 28 Lipoprotein lipasePseudomonas A 15 Lipoprotein lipase Pseudomonas B 24

Reaction conditions were as described in Table 1, with one modification,namely caprylic acid (0.28 gr) was used as the fatty acid.

Table 2 shows that lipases extracted from Candida Antarctica, Mucormiehei, Pseudomonas Cepacia, Rhizopus arrhizus, Mucor javanicus,Rhizomucor miehei, Chromobacterium viscosum and Lipoprotein lipasePseudomonas A show reasonable acidolysis activity using Caprylic acidand MCT as starting materials.

Tables 3-9 herein below also show that the most active lipases tocatalyze the reaction between MCT and FFA include mainly the enzymesextracted from the aforementioned group of microorganisms. These resultsindicate that such lipases are efficient for acidolysis reactions wherethe substrates are MCT and FFA providing that the fatty acid issaturated, mono-unsaturated, di-unsaturated or tri-unsaturated andconsists of 6-18 carbons.

TABLE 3 The acidolysis activity of different enzymes using MCT andCapric acid. Lipase origin Conversion % (24 h) Aspergillus niger 3Candida Antarctica 25 Candida cylindracea 8 Mucor miehei 39 Pseudomonasfluorescens 9 Pseudomonas cepacia 37 Rhizopus arrhizus 42 Rhizopusniveus 3 Porcine pancreas lipase 5 Aspergillus oryzae 15 Candidalipolytica 5 Mucor javanicus 37 Penicillium roqueforti 5 Rhizomucormiehei 37 Wheat germ 6 Chromobacterium viscosum 28 Lipoprotein lipasePseudomonas A 15 Lipoprotein lipase Pseudomonas B 24

Reaction conditions as described in Table 1, with one modification,namely capric acid (0.34 gr) was used as the fatty acid.

TABLE 4 The acidolysis activity of different enzymes using MCT andLauric acid. Lipase origin Conversion % (24 h) Aspergillus niger 5Candida Antarctica 14 Candida cylindracea 2 Mucor miehei 38 Pseudomonasfluorescens 12 Pseudomonas cepacia 17 Rhizopus arrhizus 29 Rhizopusniveus 5 Porcine pancreas lipase 6 Aspergillus oryzae 14 Candidalipolytica 8 Mucor javanicus 41 Penicillium roqueforti 7 Rhizomucormiehei 39 Wheat germ 4 Chromobacterium viscosum 31 Lipoprotein lipasePseudomonas A 17 Lipoprotein lipase Pseudomonas B 27

Reaction conditions as described in Table 1, with one modification,namely lauric acid (0.4 gr) was used as the fatty acid.

TABLE 5 The acidolysis activity of different enzymes using MCT andPalmitic acid. Lipase origin Conversion % (24 h) Aspergillus niger 3Candida Antarctica 22 Candida cylindracea 6 Mucor miehei 41 Pseudomonasfluorescens 2 Pseudomonas cepacia 31 Rhizopus arrhizus 39 Rhizopusniveus 1 Porcine pancreas lipase 1 Aspergillus oryzae 15 Candidalipolytica 5 Mucor javanicus 40 Penicillium roqueforti 2 Rhizomucormiehei 33 Wheat germ 2 Chromobacterium viscosum 31 Lipoprotein lipasePseudomonas A 15 Lipoprotein lipase Pseudomonas B 26

Reaction conditions as described in Table 1, with one modification,namely palmitic acid (0.51 gr) was used as the fatty acid.

TABLE 6 The acidolysis activity of different enzymes using MCT andStearic acid. Lipase origin Conversion % (24 h) Aspergillus niger 3Candida Antarctica 34 Candida cylindracea 5 Mucor miehei 42 Pseudomonasfluorescens 6 Pseudomonas cepacia 32 Rhizopus arrhizus 38 Rhizopusniveus 2 Porcine pancreas lipase 5 Aspergillus oryzae 9 Candidalipolytica 3 Mucor javanicus 37 Penicillium roqueforti 5 Rhizomucormiehei 37 Wheat germ 6 Chromobacterium viscosum 28 Lipoprotein lipasePseudomonas A 15 Lipoprotein lipase Pseudomonas B 30

Reaction conditions as described in Table 1, with one modification,namely stearic acid (0.56 gr) was used as the fatty acid.

TABLE 7 The acidolysis activity of different enzymes using MCT and Oleicacid. Lipase origin Conversion % (24 h) Aspergillus niger 1 CandidaAntarctica 20 Candida cylindracea 3 Mucor miehei 40 Pseudomonasfluorescens 3 Pseudomonas cepacia 37 Rhizopus arrhizus 41 Rhizopusniveus 1 Porcine pancreas lipase 4 Aspergillus oryzae 12 Candidalipolytica 1 Mucor javanicus 42 Penicillium roqueforti 2 Rhizomucormiehei 43 Wheat germ 2 Chromobacterium viscosum 33 Lipoprotein lipasePseudomonas A 17 Lipoprotein lipase Pseudomonas B 29

Reaction conditions as described in Table 1, with one modification,namely, oleic acid (0.56 gr) was used as the fatty acid.

TABLE 8 The acidolysis activity of different enzymes using MCT andLinoleic acid. Lipase origin Conversion % (24 h) Aspergillus niger 2Candida Antarctica 19 Candida cylindracea 2 Mucor miehei 41 Pseudomonasfluorescens 3 Pseudomonas cepacia 37 Rhizopus arrhizus 42 Rhizopusniveus 4 Porcine pancreas lipase 5 Aspergillus oryzae 17 Candidalipolytica 2 Mucor javanicus 33 Penicillium roqueforti 3 Rhizomucormiehei 35 Wheat germ 4 Chromobacterium viscosum 20 Lipoprotein lipasePseudomonas A 12 Lipoprotein lipase Pseudomonas B 17

Reaction conditions as described in Table 1, with one modification,namely linoleic acid (0.55 gr) was used as the fatty acid.

TABLE 9 The acidolysis activity of different enzymes using MCT andalpha-Linolenic acid. Lipase origin Conversion % (24 h) Aspergillusniger 1 Candida Antarctica 15 Candida cylindracea 2 Mucor miehei 31Pseudomonas fluorescens 2 Pseudomonas cepacia 35 Rhizopus arrhizus 37Rhizopus niveus 1 Porcine pancreas lipase 6 Aspergillus oryzae 12Candida lipolytica 2 Mucor javanicus 22 Penicillium roqueforti 3Rhizomucor miehei 39 Wheat germ 3 Chromobacterium viscosum 15Lipoprotein lipase Pseudomonas A 13 Lipoprotein lipase Pseudomonas B 12

Reaction conditions as described in Table 1, with one modification,namely alpha-linolenic acid (0.55 gr) was used as the fatty acid.

TABLE 10 The acidolysis activity of different enzymes using MCT andArachidonic acid. Lipase origin Conversion % (24 h) Aspergillus niger 3Candida Antarctica 10 Candida cylindracea 3 Mucor miehei 3 Pseudomonasfluorescens 6 Pseudomonas cepacia 19 Rhizopus arrhizus 2 Rhizopus niveus5 Porcine pancreas lipase 2 Aspergillus oryzae 6 Candida lipolytica 2Mucor javanicus 6 Penicillium roqueforti 4 Rhizomucor miehei 15 Wheatgerm 2 Chromobacterium viscosum 12 Lipoprotein lipase Pseudomonas A 7Lipoprotein lipase Pseudomonas B 8

Reaction conditions as described in Table 1, with one modification,namely arachidonic acid (0.6 gr) was used as the fatty acid.

The results presented in Table 10 show that most lipases from thevarious sources did not catalyze the acidolysis of arachidonic acid andMCT as efficiently as in the other experiments disclosed hereinabove.This low acidolysis activity for the different lipases is common incircumstances where the fatty acid substrate contains high degree ofunsaturation such that present in ARA, EPA and DHA. The results in Table10 show that lipases extracted from Pseudomonas cepacia, Rhizomucormiehei, Candida antarctica and Chromobacterium viscosum are among themost efficient enzymes for the incorporation of ARA into MCT substrates.Lipases extracted from Pseudomonas cepacia and Chromobacterium viscosumare not certified for food applications, and therefore, the other twolipases are being used for acidolysis of ARA and MCT.

TABLE 11 The acidolysis activity of different enzymes using MCT and EPA.Lipase origin Conversion % (24 h) Aspergillus niger 2 Candida Antarctica22 Candida cylindracea 3 Mucor miehei 25 Pseudomonas fluorescens 3Pseudomonas cepacia 25 Rhizopus arrhizus 22 Rhizopus niveus 2 Porcinepancreas lipase 3 Aspergillus oryzae 14 Candida lipolytica 3 Mucorjavanicus 29 Penicillium roqueforti 7 Rhizomucor miehei 30 Wheat germ 3Chromobacterium viscosum 25 Lipoprotein lipase Pseudomonas A 6Lipoprotein lipase Pseudomonas B 14

Reaction conditions as described in Table 1, with one modification,namely EPA (0.6 gr) was used as the fatty acid.

TABLE 12 The acidolysis activity of different enzymes using MCT and DHA.Lipase origin Conversion % (24 h) Aspergillus niger 2 Candida Antarctica24 Candida cylindracea 2 Mucor miehei 27 Pseudomonas fluorescens 3Pseudomonas cepacia 19 Rhizopus arrhizus 21 Rhizopus niveus 3 Porcinepancreas lipase 5 Aspergillus oryzae 2 Candida lipolytica 3 Mucorjavanicus 2 Penicillium roqueforti 5 Rhizomucor miehei 16 Wheat germ 6Chromobacterium viscosum 12 Lipoprotein lipase Pseudomonas A 11Lipoprotein lipase Pseudomonas B 10

Reaction conditions as described in Table 1, with one modification,namely DHA (0.65 gr) was used as the fatty acid.

Tables 11 and 12 show that some lipases exhibit reliable acidolysisactivity for EPA and DHA when both were separately interesterified withMCT. The results presented in Tables 11 and 12 show that lipasesextracted from Candida Antarctica, Mucor miehei, Pseudomonas Cepacia,Rhizopus arrhizus, and Rhizomucor miehei are the most efficient enzymesfor incorporation of DHA and EPA into MCT.

These results demonstrate that long-chain fatty acyl groups of differenttypes can be efficiently incorporated in the sn-1 position of MCTmolecules by using different lipases adapted to applications in organicmedia. The most active lipases that are certified for food applicationsand exchange medium-chain fatty acyl groups bound on the sn-1 positionof MCT molecules with long-chain fatty acyl groups were identified andinclude those extracted from Candida antarctica, Mucor miehei, Rhizopusarrhizus, Mucor javanicus, Rhizomucor miehei, Thermomyces lanuginose andLipoprotein lipase Pseudomonas A. The present results also demonstratethat the incorporation of polyunsaturated FAs (PUFAs) in MCT moleculesis also possible using the adapted reaction system with adapted enzymesfor organic synthesis.

Example 2 Synthesis of Structured Triglycerides

The acidolysis or inter-esterification reaction is initiated by adding 1g immobilized lipase preparation to 10 g MCT and an equimolar amount ofa free fatty acid or fatty acid ethyl ester. The reaction mixture isshaken at 50° C. for 2 to 8 hours. The immobilized enzyme is usedrepeatedly, i.e., the reaction is continued by leaving the immobilizedenzyme in the reaction vessel after completion of the reaction, andreplacing the reaction mixture with a freshly prepared reaction mixturecomprising an MCT and a fatty acid or fatty acid ethyl ester.Thereafter, the triglyceride mixture is isolated using a moleculardistillation system where the first distilled fraction at a temperatureof 120° C. and a vacuum of 0.005 mmHg contains mainly the medium- andlong-chain free fatty acids or their ethyl esters and partly thenon-reacted MCT. The excess MCT in the medium is distilled at 200° C.and a pressure of 0.005 mmHg. The resulting oil contains mainly reactedMCT with one long-chain fatty acid at the sn-1 position (up to 80%) andalso contains reacted MCT with two long-chain fatty acyl groups at thesn-1 and sn-3 positions. To protect the oil from oxidation, alphatocopherol is added (2 mg per 1 g of structured oil) into the structuredoil. This oil is sterilized prior to emulsification by filtrationthrough a sterilizing filter (pore size 0.2 μm).

Example 3 Preparation of Structure Triglycerides of PredeterminedContent of Fatty Acids

The starting material MCTs composed of 58.3% C8 and 41.7% C10 (100 g,0.2 mol) was mixed with a donor of a specific long-chain fatty acid,preferably a free fatty acid or ethyl fatty acid ester (0.24 mol). Thesolution was heated to 55° C. to obtain a homogenous mixture. A lipase(10 g) of 1,3-positional specificity, such as Lipozyme RM IM or anyother lipase preparation was added to the reaction mixture. The reactionmixture was shaken at 55° C. for 8 hours. The enzyme was filtered offfrom the reaction medium for repeated use. The filtrate was subjected tomolecular distillation where the first fraction was collected at atemperature of 120° C. and a pressure of 0.005 mmHg, which containedmainly the non-reacted fatty acids and the medium-chain fatty acidsproduced in the reaction. The second fraction was collected at atemperature of 200° C. and a pressure of 0.005 mmHg, which containedmainly the non-reacted MCTs. The residue of the distilled reactionmixture (approximately 90 g) mainly contained the MCTs predominantlymonoacylated at the sn-1 position with the specific long-chain fattyacid (80-90%) and the MCTs predominantly diacylated at the sn-1 and sn-3position (10-20%) with the specific long-chain fatty acid present in thestarting material. Different proportions of reaction residues were mixedtogether to obtain the desired structured triglycerides composition withregard to the type, concentration and position on the glycerol backbonefor the attached fatty acid. Alpha-tocopherol (2 mg/1 g of oil) wasadded to the structured triglycerides mixture prior to emulsification.

Example 4 Preparation of Structured Triglyceride Mixture ContainingArachidonic Acid

MCTs (100 g, 0.2 mol) and either Arachidonic acid (0.24 mol, free acidor its ethyl ester) or Martek's oil containing ARA and DHA eachapproximately 20% (50 g) were mixed together to obtain a homogenoussolution. A lipase (10 g) of 1,3-positional specificity, such asLipozyme RM IM or any other lipase preparation was added to the reactionmixture. The reaction mixture was shaken at 50° C. for 8 hours. Theenzyme was filtered off from the reaction medium for repeated use. Thefiltrate was subjected to molecular distillation where the firstfraction was collected at a temperature of 120° C. and a pressure of0.005 mmHg, which contained mainly the unreacted fatty acids or theirethyl esters and the medium-chain fatty acids produced in the reaction.The second fraction was collected at a temperature of 200° C. and apressure of 0.005 mm Hg, which contained mainly the non-reacted MCTs.The residue (approximately 90 g) mainly contained the MCTs predominantlymonoacylated at the sn-1 position with the specific long-chain fattyacid (80-90%) and the MCTs predominantly diacylated at the sn-1 and sn-3position (10-20%) with the specific long-chain fatty acid present in thestarting material.

Example 5 Preparation of an Emulsion Comprising the StructuredTriglycerides

200 g of the structured triglyceride preparation were prepared in alarge volume according to the procedure disclosed hereinabove (Example2). The structured triglycerides preparation was added to a homogenizedmixture comprised of 22.5 g glycerol, 12 g phospholipid (Lipoid E 80)and 765.5 g distilled water adjusted to a desired pH value. The additionof sodium oleate (0.3 g) as an emulsion stabilizer into the mixture wasoptional. The mixture was homogenized several times with a homogenizer(Ultraturrax) at a rate of 10,000 rpm. In all steps adopted forpreparation of the emulsion the temperature did not exceed 70° C. Theobtained macro-emulsion was treated further in a high-pressurehomogenizer (Microfluidizer) at 2600 psi for 5 minutes at temperaturebelow 40° C. After this treatment the emulsion was passed through amembrane filter of pore size of 0.2 μm.

The composition of the parenteral nutrition is thus as follows:

-   -   Structured triglycerides—20% (w/v)    -   Alpha tocopherol—1.8 mg/1 g fatty acids    -   Phospholipids—12 g/liter    -   Glycerin—25 g/L    -   Water to complete to 1 liter.

After filling 200 ml aliquots of said lipid emulsion into plastic bags,the plastic bags are sterilized using high-pressure steam for 20 minutesat 121° C. to obtain a nutrition emulsion composition.

Example 6 Preparation of a Structured Triglyceride Composition

This example illustrates the fatty acid composition of structuredtriglycerides. As shown in Table 13, MCFA, LCFA, and VLCFA constitute40-50%, 35-55%, and 4.5-5.5% by weight, respectively, of total FA in thestructured triglycerides. The ratio of ω-6 to ω-3 fatty acids in thestructured triglycerides is 1.75.

TABLE 13 Fatty acid composition of structured triglycerides (% byweight). Caproic acid  6:0 0-5 Caprylic acid  8:0 20-30 Capric acid 10:010-30 Lauric acid 12:0 0-5 Myristic acid 14:0 0-5 Palmitic acid 16:0 5-30 Palmitoleic acid 16:1 0-5 Stearic acid 18:0 0-5 Oleic acid 18:110-30 Linoleic acid 18:2 ω-6 10-30 Alpha linolenic acid 18:3 ω-3  5-15Arachidonic acid (AA) 20:4 ω-6 1-5 Ecosapentaenoic acid (EPA) 20:5 ω-30-5 Docosahexaenoic acid (DHA) 22:6 ω-3 1-5

Example 7 Preparation of a Structured Triglyceride Composition

This example illustrates the fatty acid composition of structuredtriglycerides. As shown in Table 14, MCFA, LCFA, and VLCFA constitute45, 50.5, and 4.5% by weight, respectively, of total FA in thestructured triglycerides. The ratio of ω-6 to ω-3 fatty acids in thestructured triglycerides is 1.75.

TABLE 14 Fatty acid composition of structured triglycerides (%). Caproicacid  6:0 2.5 Caprylic acid  8:0 30 Capric acid 10:0 10 Lauric acid 12:02.5 Palmitic acid 16:0 10 Stearic acid 18:0 2.5 Oleic acid 18:1 15Linoleic acid 18:2 ω-6 16 Alpha linolenic acid 18:3 ω-3 7 Arachidonicacid (AA) 20:4 ω-6 1.5 Ecosapentaenoic acid (EPA) 20:5 ω-3 1.5Docosahexaenoic acid (DHA) 22:6 ω-3 1.5

It will be appreciated by persons skilled in the art that the presentinvention is not limited by what has been particularly shown anddescribed herein above. Rather the scope of the invention is defined bythe claims that follow.

1. A structured triglyceride comprising a glycerol backbone having threefatty acid residues esterified thereto, wherein two fatty acid residuesselected from the group consisting of C₆-C₁₂ fatty acids and activederivatives thereof are esterified to the internal position and to afirst external position of the triglyceride backbone, and one fatty acidresidue selected from the group consisting of C₁₄-C₁₈ fatty acids,C₂₀-C₂₂ fatty acids, and active derivatives thereof is esterified to asecond external position of the triglyceride backbone.
 2. The structuredtriglyceride according to claim 1, wherein the C₁₄-C₁₈ fatty acids areselected from the group consisting of myristic acid, palmitic acid,palmitoleic acid, stearic acid, oleic acid, linoleic acid, alphalinolenic acid, and any combination thereof.
 3. The structuredtriglyceride according to claim 1, wherein the C₂₀-C₂₂ fatty acids areselected from the group consisting of arachidonic acid, eicosapentaenoicacid, docosahexaenoic acid, and any combination thereof.
 4. Thestructured triglyceride according to claim 1, wherein the C₁₄-C₁₈ fattyacids and the C₂₀-C₂₂ fatty acids are selected from the group consistingof ω-3, ω-6, ω-9 fatty acids, and any combination thereof.
 5. Aparenteral nutrition emulsion composition comprising a structuredtriglyceride according to claim
 1. 6. The parenteral nutrition emulsioncomposition according to claim 5, wherein the structured triglyceride ispresent in an amount of about 80% to about 100% of total triglyceridesof said emulsion.
 7. The parenteral nutrition emulsion compositionaccording to claim 5, wherein the C₁₄-C₁₈ fatty acids and the C₂₀-C₂₂fatty acids are selected from the group consisting of ω-3, ω-6, ω-9fatty acids, and any combination thereof.
 8. The parenteral nutritionemulsion composition according to claim 5, comprising from about 9% toabout 90% by weight C₆-C₁₂ fatty acids based on the weight of totalfatty acids.
 9. The parenteral nutrition emulsion composition accordingto claim 5, comprising from about 9% to about 90% by weight C₁₄-C₁₈fatty acids based on the weight of total fatty acids.
 10. The parenteralnutrition emulsion composition according to claim 5, comprising fromabout 1% to about 10% by weight C₂₀-C₂₂ fatty acids based on the weightof total fatty acids.
 11. The parenteral nutrition emulsion compositionaccording to claim 7, wherein the ω-6 fatty acids and the ω-3 fattyacids are in a ratio of about 7:1 to about 1:1.
 12. The parenteralnutrition emulsion composition according to claim 5, wherein thestructured triglyceride constitutes from about 10% to about 40% (w/v) ofthe composition.
 13. The parenteral nutrition emulsion compositionaccording to claim 5, wherein a droplet size of said emulsion is lowerthan about 1 μm.
 14. The parenteral nutrition emulsion compositionaccording to claim 5, further comprising tocopherol.
 15. The parenteralnutrition emulsion according to claim 14, wherein the tocopherol isalpha tocopherol.
 16. The parenteral nutrition emulsion according toclaim 5, further comprising at least one component selected from thegroup consisting of emulsifiers, surfactants, carbohydrates, vitamins,amino acids, trace minerals, osmolality modifiers and water.
 17. Theparenteral nutrition emulsion according to claim 5 comprising: (a) 20%(w/v) structured triglycerides comprising: about 40-50% by weight C₆-C₁₂fatty acids based on the weight of total fatty acids, wherein the C₆-C₁₂fatty acids comprise 0-5% caproic acid, 20-30% caprylic acid, 10-30%capric acid, and 0-5% lauric acid by weight based on the weight of totalfatty acids; about 35-55% by weight C₁₄-C₁₈ fatty acids based on theweight of total fatty acids, wherein the C₁₄-C₁₈ fatty acids comprise0-5% mystiric acid, 5-30% palmitic acid, 0-5% palmitoleic acid, 0-5%stearic acid, 10-30% oleic acid, 10-30% linoleic acid, and 5-15% alphalinolenic acid by weight based on the weight of total fatty acids; andabout 1-10% C₂₀-C₂₂ by weight fatty acids based on the weight of totalfatty acids, wherein the C₂₀-C₂₂ fatty acids comprise 1-5% AA, 0-5% EPA,and 1-5% DHA by weight based on the weight of total fatty acids, whereinthe ratio of ω-6 to ω-3 fatty acids is 1:1-2:1; (b) 1.2% (w/v)phospholipids; (c) 1.8-2.0 mg/1 g of fatty acids alpha tocopherol; (d)0-25 g/L glycerin; and (e) water.
 18. The parenteral nutrition emulsioncomposition according to claim 5 comprising: (a) about 20% (w/v)structured triglycerides comprising: about 45% by weight C₆-C₁₂ fattyacids based on the weight of total fatty acids, wherein the C₆-C₁₂ fattyacids comprise 2.5% caproic acid, 30% caprylic acid, 10% capric acid,and 2.5% lauric acid by weight based on the weight of total fatty acids;about 50% by weight C₁₄-C₁₈ fatty acids based on the weight of totalfatty acids, wherein the C₁₄-C₁₈ fatty acids comprise 10% palmitic acid,2.5% stearic acid, 15% oleic acid, 16% linoleic acid, and 7% alphalinolenic acid by weight based on the weight of total fatty acids; andabout 5% by weight C₂₀-C₂₂ fatty acids based on the weight of totalfatty acids, wherein the C₂₀-C₂₂ fatty acids comprise 1.5% AA, 1.5% EPA,and 1.5% DHA by weight based on the weight of total fatty acids, whereinthe ratio of ω-6 to ω-3 fatty acids is 1.75; (b) about 1.2% (w/v)phospholipids; (c) about 1.8 mg/1 g of fatty acids alpha tocopherol; (d)about 10-25 g/L glycerin; and (e) water.
 19. A process of synthesizing astructured triglyceride according to claim 1 comprising the step ofperforming an acidolysis reaction.
 20. The process according to claim19, wherein the acidolysis reaction is catalyzed by a lipase.
 21. Theprocess according to claim 19, wherein the triglyceride is a mediumchain triglyceride.
 22. The process according to claim 19, wherein thefatty acid is selected from the group consisting of C₁₄-C₁₈ fatty acids,C₂₀-C₂₂ fatty acids, and active derivatives thereof.
 23. The processaccording to claim 19 further comprising a step of distilling thereaction mixture to remove non-reacted medium chain triglyceride andfatty acid.
 24. A process of preparing a parenteral nutrition emulsioncomposition according to claim 5 comprising the step of reducing thedroplet size of the emulsion below of about 1 μm.
 25. A method ofproviding nutrition to a subject in need thereof comprising parenterallyadministering to the subject a parenteral nutrition emulsion compositionaccording to claim
 5. 26. The method according to claim 25, wherein thesubject is a preterm infant, a term infant, a child, an adult, acritically ill patient, a cancer patient, or a patient suffering fromone of the conditions selected from trauma, burns, malnutrition,starvation, aging, and immunosuppression.
 27. The method according toclaim 25, wherein the subject is an AIDS patient.